Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$175.99	5.351%	$185.4072	$185.41	$185.40	$185.40
Purchase #2	$28.82	11.872%	$32.2415	$32.24	$32.25	$32.20
Purchase #3	$187.91	4.656%	$196.6591	$196.66	$196.65	$196.70
Purchase #4	$125.49	12.749%	$141.4887	$141.49	$141.50	$141.50
Purchase #5	$173.80	6.424%	$184.9649	$184.96	$184.95	$185.00
Purchase #6	$49.47	4.326%	$51.6101	$51.61	$51.60	$51.60
Purchase #7	$163.72	3.134%	$168.851	$168.85	$168.85	$168.90
7 purchase totals =	$905.20		$961.2225	$961.22	$961.20	$961.30